When making a phone call from a calling party terminal to a called party terminal, the called party is alerted of the incoming call by a ring signal while the calling party hears a ring back signal until the call is answered or terminated. A called party and a calling party are typically human beings also known as users operating a respective device like a stationary or mobile phone or stationary or laptop computer. A ring signal is any kind of signal for alerting the called party about an incoming call. Examples for ring signals are ring tones, multimedia clips, optical signals, recorded speech, announcements, or vibration sequences that can be output at the called party terminal, e.g. via a loudspeaker, screen display, Light Emitting Diodes (LEDs), vibration mechanics etc.
For the ring signal output to the called party, current typical implementation is that ring signals are stored in the called party terminal and the called party can select the ring signal to be played during the alerting period. The called party has the possibility to assign different calling party phone numbers to different ring signals and to store these relations in the called party's terminal. When an incoming call is received and the received phone number of the calling party matches to one of the stored phone numbers, the corresponding ring signal is output.
For the ring back signal played to the calling party terminal, it is possible that the ring back signal can be either generated by the calling party terminal itself or received from the network. If the ring back signal is received from the network it can be either the default ring back signal stored in a network node or a ring back signal specified by the called party. The latter service is also known as “Personalized Ring Back Tone (PRBT)”. The PRBT service enables the calling party to specify a ring tone that is played-back at call-attempt to the calling party.
Hence, many call procedures exist wherein a party can specify its own ring signal for improved information or entertainment purpose. However, little is known about procedures wherein a calling party can specify a ring signal to be output at a called party terminal for alerting the called party regarding the call from the calling party.
CN 1859480 A describes a method and system for providing a ring signal called multiple color alerting tone (CAT) to a called party. A user having the future role of a calling party or a called party can subscribe to a CAT service by sending from a terminal CAT instructions to a Session Initiation Protocol (SIP)-based softswitch server. The terminal can be a web terminal, an interactive communication terminal or an interactive voice responder device. For the subscription, the softswitch server indicates to the user to select a ring signal and to input a called party or a calling party number, and/or groups. At the terminal, a ring signal, a called party or a calling party number and/or group numbers are selected and the selected ring signal and numbers are sent from the terminal to the softswitch server which records the submitted subscription information.
When the calling party makes a call from a calling party terminal to a called party terminal of a called party via the softswitch server, the softswitch server checks if the CAT service is subscribed. If the check is in the affirmative, the softswitch server sends a CAT request to a media server and a CAT request to a called party terminal to establish a connection between each other and then to send a ring signal from the media server to the called party terminal.
The softswitch server in CN 1859480 A may control the sending of the request to the media server as well the sending of the request to the called party terminal, however, the softswitch server does not control the sending of the ring signal from the media server to the called party terminal. The softswitch server does not control which ring signal is actually sent and at what time exactly. Hence, it may occur that an incorrect ring signal is sent or that the timing of the sending of the ring signal from the media server to the called party terminal does not match to further processes or message exchanges performed at call attempt time which may lead to unsuccessful call attempts and poor user satisfaction. Furthermore, not every called party terminal is capable of establishing two connections, i.e. one for the delivery of the ring signal and one for the call attempt.